Provided are: steel for knives, having a higher hardness and better corrosion resistance than conventional steel for knives; a knife; steel for martensitic knives; and a production method for same. The steel for knives comprises a component composition containing, in mass %, 0.55 to 0.95% C, 0.1 to 0.49% Si, 0.1%-1.5% Mn, 9.0 to 10.2% Cr, and 0.5%-3.0% of either Mo or W or a complex of both (Mo+W/2), with the remainder being Fe and unavoidable impurities.